Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1998-04-03
2001-02-20
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S551000, C250S21400C
Reexamination Certificate
active
06191411
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric conversion apparatus for forming an image by a radioactive ray such as a visible light or an X-ray, and for example, to a photoelectric conversion apparatus adapted to be used for a photoelectric conversion apparatus of one-dimension or two-dimension such as a still camera or a radioactive-ray image pickup apparatus.
2. Description of the Related Art
In convention, as said to be a photograph, a silver-salt photograph which uses an optical camera and a silver-salt film has occupied the major portion of the photographs. Even though the semiconductor technologies have been developed and the photoelectric conversion apparatuses have been developed which are capable of taking pictures of the images of motion pictures such as a video cam corder by using a solid state image sensing device using a Si single crystal as represented by the CCD type sensor, the MOS type sensor, these images can not be better than the silver-salt photograph with respect to the number of pixels as well as to the S/N ratio, and thus it has been common to use the silver-salt photographs for taking the static images thereinto.
Recently, the demands for image processing by a computer, a retention by an electronic file, and an image transmission by electronic mail have increased, and it is desired to have an electronic image pickup apparatus which outputs as a digital signal of similar quality to the silver-salt photograph image. This can be equally applied to not only the general photographs but also the fields of medical service and non-destructive inspection.
In the field of medical service an X-ray photograph is known as the one that uses a silver-salt photograph technology. This is the one in which an X-ray radiated from an X-ray source is irradiated to the diseased part of a human body, and with the information of that transmission, for example, it judges whether or not there is a broken bone or a tumor, and has been used for the medical diagnoses for a long time. (This can be said to be one the non-destructive inspections). Usually, the X-ray transmitted through the diseased part is to be incident once on a wavelength conversion unit such as a fluorescent material, and is converted to a light of the sensitive wave region such as a visible light, and then is exposure on the silver-salt film. Although the silver-salt film has advantages such as the silver-salt film has a goood sensitivity, and also has a high quality of resolution, but it has problems such as taking too much time for a development, taking a lot of time and labor for a retention/a management, and not readily to transmitted to a remote area, and the like, and thus it is desired to have an electronic X-ray image pickup apparatus which outputs the digital signal not of similar quality to the silver-salt photograph image as described above.
However, there still remains some points which should be improved in order to electronically read the X-ray images or the images converted from the X-rays and to use them as data for the medical service and/or non-destructive testing.
That is, it is needed to consider the problems of noises which could be added to the data, when adopting the electronic data. By adopting the noises with the image data, there is the possibility of resulting damage to the the medical diagnoses and/or the diagnoses of the structures by the non-destructive inspections.
Further, not only for the problem of noise, but also for reducing an exposure quantity to the human body, much high sensitive photo-electric conversion apparatus is required.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a photoelectric conversion apparatus with the reduced noise and the high sensitivity, and its system.
Another object of the present invention is to provide a photoelectric conversion apparatus comprising:
a photoelectric conversion unit having a drive detection circuit for driving a sensor substrate of which a plurality of photoelectric conversion elements are arranged on an insulating substrate and said photoelectric conversion elements, and for detecting signals from said photelectric conversion elements; and
a control unit for controlling said photoelectric conversion unit,
wherein a reference electrical potential of said photoelectric conversion unit and a reference electrical potential of said control unit are alternate-currently separated.
Yet another object of the present invention is to provide a photoelectric conversion system comprising:
a photoelectric conversion unit;
said photoelectric conversion unit having a plurality of photoelectric conversion elements, a drive detection circuit being driven with a first reference electrical potential for driving said photoelectric conversion elements and for obtaining outputs from said photoelectric conversion elements,
a control unit;
said control unit having a circuit, being provided separately from said photoelectric conversion unit and being driven with a second reference electrical potential for controlling said photoelectric conversion unit,
wherein, said first reference electrical potential and said second reference electrical potential are alternate-currently separated such that a frequency equal to or more than a frequency corresponding to a read cycle of said photoelectric conversion unit is removed.
For an electronification of an X-ray image pickup apparatus, for example, it has been considered a development of a photoelectric conversion apparatus using large-scale sensors of which image pickup elements using photoelectric conversion elements of hydrogenated amorphours-silicon (hereinafter, referred to as a-Si) on an insulating substrate are arranged in two-dimensions. The photoelectric conversion apparatus of this type is capable of individually detecting charges flown in a reversed direction of an individual diode, by forming semiconductor diodes by depositing metals and/or a-Si on an insulating substrate whose edge is about 30-50 cm by using a sputtering apparatus and/or a chemical vapor deposition apparatus (CVD apparatus) and the like, and then by applying an electric field of a reversed bias to the semiconductor diodes of the numbers of 2000×2000, by also a thin-film transistor (hereinafter, referred to as a TFT) simultaneously formed-in. Since it is well known that a photocurrent which corresponds to a light quantity incident on the semiconductor layer will flow by applying an electric field of a reversed direction to a semiconduuctor diode, this is utilized therefor. In contrast to a photoelectric conversion apparatus with a single crystal, which can be formed in a small size only, because the a-Si can form the photoelectric conversion elements on such a large area whose one edge is 30-50 cm, the photoelectric conversion apparatus with a size equivalent to a size of a diseased part of a human body is possible, thereby using a lens and the like without using a minature optical system, directly forming a wavelength conversion unit such as a fluorescent material and the like on the image pickup elements, and a light which is converted (in particular efficiently) to a detectable wavelength of the photoelectric conversion element, emitted by the fluorescent material, can be utilized with a high efficiency. Further, it is possible to directly detect the X-ray by the layer within the photoelectric conversion element without using the fluorescent material if taking the design of the light receiving area into consideration.
When forming an image by using the minature optical system in the phtoelectric conversion apparatus of the small size which uses the single crystal, only about {fraction (1/1000)} of the light emitted from the fluorescent material can be utilized because of the loss of the optical system and the like. Also, in case of observing the human body with the X-ray, it is required to take a photograph thereof with as weak an X-ray as possible. Accordingly, it is very difficult to implement a high quality X-ray diagnostic appa
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee John R.
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